/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_sparse_q7.c
*
* Description:	Q7 sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* ------------------------------------------------------------------- */
#include "arm_math.h"


/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Sparse
 * @{
 */


/**
 * @brief Processing function for the Q7 sparse FIR filter.
 * @param[in]  *S           points to an instance of the Q7 sparse FIR structure.
 * @param[in]  *pSrc        points to the block of input data.
 * @param[out] *pDst        points to the block of output data
 * @param[in]  *pScratchIn  points to a temporary buffer of size blockSize.
 * @param[in]  *pScratchOut points to a temporary buffer of size blockSize.
 * @param[in]  blockSize    number of input samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 32-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.7 format and multiplications yield a 2.14 result.
 * The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * The accumulator is then converted to 18.7 format by discarding the low 7 bits.
 * Finally, the result is truncated to 1.7 format.
 */

void arm_fir_sparse_q7(
    arm_fir_sparse_instance_q7* S,
    q7_t* pSrc,
    q7_t* pDst,
    q7_t* pScratchIn,
    q31_t* pScratchOut,
    uint32_t blockSize)
{

	q7_t* pState = S->pState;                      /* State pointer */
	q7_t* pCoeffs = S->pCoeffs;                    /* Coefficient pointer */
	q7_t* px;                                      /* Scratch buffer pointer */
	q7_t* py = pState;                             /* Temporary pointers for state buffer */
	q7_t* pb = pScratchIn;                         /* Temporary pointers for scratch buffer */
	q7_t* pOut = pDst;                             /* Destination pointer */
	int32_t* pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
	uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
	uint16_t numTaps = S->numTaps;                 /* Filter order */
	int32_t readIndex;                             /* Read index of the state buffer */
	uint32_t tapCnt, blkCnt;                       /* loop counters */
	q7_t coeff = *pCoeffs++;                       /* Read the coefficient value */
	q31_t* pScr2 = pScratchOut;                    /* Working pointer for scratch buffer of output values */
	q31_t in;


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q7_t in1, in2, in3, in4;

	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_q7(py, (int32_t) delaySize, &S->stateIndex, 1, pSrc, 1,
	                     blockSize);

	/* Loop over the number of taps. */
	tapCnt = numTaps;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
	                    (int32_t) blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	/* Loop over the blockSize. Unroll by a factor of 4.
	 * Compute 4 multiplications at a time. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	 * compute the remaining samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
		                    (int32_t) blockSize, 1, blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pScratchOut = pScr2;

		/* Loop over the blockSize. Unroll by a factor of 4.
		 * Compute 4 MACS at a time. */
		blkCnt = blockSize >> 2;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* If the blockSize is not a multiple of 4,
		 * compute the remaining samples */
		blkCnt = blockSize % 0x4u;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex = ((int32_t) S->stateIndex -
		             (int32_t) blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* All the output values are in pScratchOut buffer.
	   Convert them into 1.15 format, saturate and store in the destination buffer. */
	/* Loop over the blockSize. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u) {
		in1 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
		in2 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
		in3 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
		in4 = (q7_t) __SSAT(*pScr2++ >> 7, 8);

		*__SIMD32(pOut)++ = __PACKq7(in1, in2, in3, in4);

		/* Decrement the blockSize loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,
	   remaining samples are processed in the below loop */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		*pOut++ = (q7_t) __SSAT(*pScr2++ >> 7, 8);

		/* Decrement the blockSize loop counter */
		blkCnt--;
	}

#else

	/* Run the below code for Cortex-M0 */

	/* BlockSize of Input samples are copied into the state buffer */
	/* StateIndex points to the starting position to write in the state buffer */
	arm_circularWrite_q7(py, (int32_t) delaySize, &S->stateIndex, 1, pSrc, 1,
	                     blockSize);

	/* Loop over the number of taps. */
	tapCnt = numTaps;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
	                    (int32_t) blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	/* Loop over the blockSize */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* Perform multiplication and store in the scratch buffer */
		*pScratchOut++ = ((q31_t) * px++ * coeff);

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Load the coefficient value and
	 * increment the coefficient buffer for the next set of state values */
	coeff = *pCoeffs++;

	/* Read Index, from where the state buffer should be read, is calculated. */
	readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

	/* Wraparound of readIndex */
	if(readIndex < 0) {
		readIndex += (int32_t) delaySize;
	}

	/* Loop over the number of taps. */
	tapCnt = (uint32_t) numTaps - 1u;

	while(tapCnt > 0u) {
		/* Working pointer for state buffer is updated */
		py = pState;

		/* blockSize samples are read from the state buffer */
		arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
		                    (int32_t) blockSize, 1, blockSize);

		/* Working pointer for the scratch buffer of state values */
		px = pb;

		/* Working pointer for scratch buffer of output values */
		pScratchOut = pScr2;

		/* Loop over the blockSize */
		blkCnt = blockSize;

		while(blkCnt > 0u) {
			/* Perform Multiply-Accumulate */
			in = *pScratchOut + ((q31_t) * px++ * coeff);
			*pScratchOut++ = in;

			/* Decrement the loop counter */
			blkCnt--;
		}

		/* Load the coefficient value and
		 * increment the coefficient buffer for the next set of state values */
		coeff = *pCoeffs++;

		/* Read Index, from where the state buffer should be read, is calculated. */
		readIndex =
		    ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

		/* Wraparound of readIndex */
		if(readIndex < 0) {
			readIndex += (int32_t) delaySize;
		}

		/* Decrement the tap loop counter */
		tapCnt--;
	}

	/* All the output values are in pScratchOut buffer.
	   Convert them into 1.15 format, saturate and store in the destination buffer. */
	/* Loop over the blockSize. */
	blkCnt = blockSize;

	while(blkCnt > 0u) {
		*pOut++ = (q7_t) __SSAT(*pScr2++ >> 7, 8);

		/* Decrement the blockSize loop counter */
		blkCnt--;
	}

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**
 * @} end of FIR_Sparse group
 */
